Furnace grate stoker control



ug 1, 1933. w. A. LACKE FURNACE GRATE STOKER CONTROL Filed Nov'. 2, 1928s sheets-sheet 1 MUH|| w. A. L AcKE 1,920,572

FURNACE GRATE STOKER CONTROL 3 Sheets-Sheet 2 Filed Nov. 2, 1928 Aug l,1933. w. A. LAcKE 92572 FURNCE @RATE STOKER CONTROL Filed Nov. 2, 1928Patented Aug. l, 1933 UNITED STATES -PATENT OFFICE mesne assignments, toPullman Car & Manufacturing Corporation, a Corporation of DelawareApplication November 2, 1928 Serial No. 316,704

4 Claims.

The invention relates generally to devices for feeding coal to furnacesequipped with Achain grate stokers, and has particular reference tomeans for automatically regulating the length of the re on the stoker.

The invention further contemplates the use of audible or visual signaldevicescontrolled by the means regulating the length of the re.

Another object of the invention is to provide a thermal unit adjacentthe discharge end of the stoker and within the heat zone of hot coals orashes passing from the stoker to the ash-pit and adapted to be affectedby the radiant energy emanating therefrom.

A still further object is to so form and dispose thethermal unit andmounting therefor that the sensitivity of `the device to the radiantenergy of the hot ashes and coals will'not be too greatly alected by theheat in the ash-pit.

The foregoing and other objects are attained by the mechanismillustrated in the accompanying drawings, in which Fig. 1 is a verticalsection through a boiler of the water tube type equipped with a chaingrate stoker and fitted with the control mechanism of the invention;

Figs. 2 and 3 are side and end elevational views, respectively, of thestoker operating mechanism;

Fig. 4 shows the electrical connection between a thermostat and thestoker operating 'mechanism; and

Figs. 5 and 6 are plan and side elevational views of a thermostat andits mounting supported from the furnace wall.

In stokers heretofore used a great loss of fuel resulted from theinability of the operator to properly regulate the speed of the stokerto maintain the fire at its highest eciency. This difficulty has beenovercome by the present invention in which mechanism has been providedto automatically accelerate or decelerate the speed of the Stokerthrough the medium of an automatic control unit responsive to heatradiations 5 and electrically connected to a solenoid4 operable toengage or disengage a ratchet operating pawl for the purpose ofshortening or lengthening the nre on the stoker. The stoker mechanism isoperable at two speeds, one too fast, if maintained,.and causing the hotcoals to be wasted into the ash-pan, and the other too slow to keep thefire against the waterback of the boiler. :v

'Ihe mechanism for effecting the change from one speed of the stoker tothe other is indicated in the drawings, in which 10 represents a watertube boiler of any approved type having the usual waterback 11 arrangedimmediately above a re bed 12 carried upon a chain grate stoker 13 fedfrom coal hopper 7.

In the present embodiment, the stoker is operated by an electric motor14 having a pinion 60 15 engaging a gear wheel 16 mounted upon drivingshaft' 17 carrying a pair of eccentrics 18 havilng link connection withratchet operating levers The eccentrics rotate in strap frames 20 hav-65 ing link extensions 21 pivoted at their ends to ratchet operatingLlevers 19 by pins 22 as best indicated in Figs. 2 and' 3. Theeccentrics are relatively offset to cause alternate oscillating movementof ratchet levers 19. The leversl 19 70 carry pawls 23 adapted forengagement with respective ratchet wheels 24 fixed to transmission shaft25 to which is secured a worm gear 26 designed to mesh with a gear wheel27 on Stokeractuating shaft 28. For the purpose of eiecting a change ingrate speed hereinbefore noted, and thereby control the length of thefire 12 on the grate 13, the pawl 23 on one of the operating levers 19is adapted to be disengaged from its ratchet 24 by means of an electromagnet or solenoid 30 carried by the lever 19 and positioned above thepawl 23 which is to be lifted by it. As shown in Figs. 2 and 3, a magnetis secured to lever 19 by a yoke piece 31 straddling the pawl andriveted astride the lever to support the magnet 30 the proper distanceabove the pawl 23 to allow it to be lifted by the magnet when energized.The lifting of the pawl will result in its disengagement from therespective ratchet 24 on shaft 25 and consequent reduction in the numberof impulses to be given said shaft, that is to say, the movement of thestoker will be reduced to its set minimum speed to prevent unconsumedfuel from being discharged into the ash-pit 32. In the embodiment shown,two levers 19 have been used, 95 operated by the respective eccentrics18 through linkextensions 21, and equipped with pawls 23 for engagingthe respective ratchets 24.

It is conceivable that within the scope of the appended claims, a singlelever 19, tted with two 10o pawls acting alternately, one of which maybe lifted out of engagement with the ratchet 24 by the solenoid 30, maybe substituted for the two lever mechanism indicated.

The magnet 30 is energized by the closing of the 105 electric' circuit 8controlled by a unit 33 located at the discharge end of the stoker 13within the radiant energy zone of the hot coals or ashes passing to theash-pit 32.

In the preferred embodiment shown. a thermostat is mounted upon theinner end of a tube 34 supported at its opposite end in the furnace wall35 and of a length that will permit the thermostat 33 to be placr d atthe medial plane of the stoker 13. The tube 34 is insulated from theheat 'of the ash-pit 32 underneath by a covering 36 of asbestos shieldedby metal sheathing 37 to protect the asbestos from thc deleteriousaction of the furnace heat and fumes of combustion. The thermostat 33rests upon a panel 38, supported upon a portion of the tube 34 cut awayfor a portion of its length as best shown in Figs. 5 and 6, leaving anextended portion 39 projecting from the base of the remainder of thetube, the panel beingheld upon the tube by screws 40 let into the tubesegment 39. The panel 38 supports the thermostat ribbon 41 at thepositive terminal 42 of the circuit with its pole piece 43 held normallyaway from the negative post 44 as indicated in Fig. 5. To preserve theintegrity of the thermostat 33 thus positionedand exposed to the dustand `heat of the ash-pitbelow it and the radiant heat of the discharginghot coals or ashes from the stoker, the tube 34 is left open to theouter air as at 45 to allow the relatively cool air to enter the tubeand sweep across the thermostat 33 and beneath the panel 38 to minimizethe effect of the enveloping heat from the ash-pit and adjacent portionof the furnace whereby the thermostat ribbon 41 is cooled and renderedmore sensitive to the relatively greater heat of the hot coals or ashespassing from the stoker 13. The air currents thus established tend alsoto carry away the stoker dust and ashes to prevent clogging andresultant failure of the ribbon 41 to respond to temperature variations.

In operation, assuming the fire bed 12 to be toc` short to be keptagainst the water back 11 of the boiler, the radiant heat from the discharging ashes from the stoker 13 will be too low to cause thermostat 33to respond to it. At this stage of operation the thremostat is out ofcontact with terminal post 44 as shown in Figs. 4 and 5, theelectromagnet 30 de-energized, and both pawls 23 operatively engagingthe ratchet wheels 24. The movement of the eccentrics 18, connected bylinks 21 to the ratchet operating levers 19, will actuate the levers tocause intermittent rotation of the worm shaft '25 through attachedratchet Wheels 24 both of which are engaged by their respective pawls23. The operation of both ratchets will accelerate the speed of theStoker 13 and continue todrive the stoker at the higher speed until thelength of the re on the stoker has sufficiently increased to extend thefire to the water-back 11 and close to the thermostat 33 when the heatemanating from the hot coals and ashes passing from the stoker willcause the ribbon 41 of the thermostat to move against the terminal post44 whereupon the circuit 8 energizing the magnet 30 and lighting thesignal lamp 9 will be closed.

The magnet 30 thus energized by the closing of the circuit 8 becomeseffective to lift adjacent pawl 23 from engagement with its ratchetwheel 24 to cause a reduction of the speed of the Stoker to the minimumset by the operation of but one pawl and ratchet mechanism since by theaction of the magnet 30 the lever carrying it vibrates idly upon theshaft 25. As the stoker continues to be driven at the lower speed underthe power of the single operating ratchet, the fire on the stoker beginsto shorten and recede from water back 11 and thermostat 33l until theheat from nant as it sweeps through the tube 34 and across the hot ashespassing from the Stoker becomes too low to operatively affect thethermostat.

As the heat radiations from the stoker decline,

the cooling effect of the outer air becomes domi- 80 the thermostatribbon 41 which then moves out of Contact with the other terminal post44, thus breaking the circuit, de-energizing the magnet and dropping thepawl 23, and extinguishing the signal lamp 9, and the cycle ofoperations repeated. The intermittent flashing of the signal 9 serves toadvise the attendant of the continuity in the cycle of operations. Anaudible signal may be substituted for the lamp 9 if desired, but thevisual signal has been found satisfactory for the purpose.

The mere placing of a thermostat at the discharge end of the stokerwould not of itself accomplish the desired result as the action of thethermostat would be too sluggish for practical purposes unless shieldedand set as described to minimize the effect of the heat in the ash-pit.

In the use of thermal control units of the type indicated in the presentembodiment it has been found necessary to adjust the distance betweenContact 43 on thermostat ribbon 41 and the terminal post 44 to X thetemperature required to move the contact 43 toward or away from the post44 to effect a change in stoker speed at predetermined lengths of thefire.

For this purpose there has been provided an adjusting mechanism operablefrom the outside of the furnace, and of simple construction andapplication. The device consists of a wheel mounted for rotationon panel38 and operatively secured by pin 49. The ribbon 41 is heldin thermostatpost 48 secured to wheel 50 by machine screws 47 properly insulated fromthe post to avoid short circuiting. The post 48 has flexible electricalconnection with terminal 42 through a brass washer 115 46 as best shownin Figs. 5 and 6. The Wheel 50 is preferably formed as a gear wheel, asindicated, and rotated by means of a worm gear 51 meshing therewith anditself actuated by a shaft 52 extending through tube 34 to the outsideof the120 furnace wall 35 and there fitted with a knurled handle 53 forconvenient manipulation of the worm. The worm is secured to a spindle 54journaled in brackets 55 on panel 38, the spindle being connected tooperating shaft 52 by a loose 125 coupling 56 to permit slight relativeangularities in positions of said shaft and spindle and to facilitatethe installation of the apparatus within the furnace.

It will be noted that by the operation of the mechanism described, theboiler is maintained at its highest efficiency and the fuel wastage heldto a minimum and to an extent impossible of attainment by methods andmachinery heretofore employed. The arrangement is simple in design andreadily and economically applied without requiring any change inexisting equipment.

What I claim is:-

l. vln grate stoker mechanism for feeding fuel through a furnace, thecombination with a con- 140 trol unit comprising a tube anchored at oneend in the wall of the furnace and having its inner end adjacent thedischarge end of 'the Stoker and a thermostat supported thereon withinthe radiant heat zone of the hot coals and ashes passing from thestoker, of means associated with said unit for shieldingthe thermostatfrom the enveloping heat of the furnace and ashpit, and a solenoid inseries with the thermostat and so placed with respect to said Stokermechanism as 50 to cause reduction of speed thereof upon closure of saidcircuit, said tube at its Wall end being open to the atmosphere wherebythe thermostat supported upon its inner end will be swept by air drawntherethrough and in the path of heated materials discharged from thestoker.

2. The combination in a furnace including an ashpit, of stoker controlmechanism for feeding fuel thru the furnace and discharging into theashpit, comprising a tube mounted n said ashpit and normally open to theatmosphere, and a thermostat controlling said mechanism supported on theinner end of said tube and exposed to the radiant heat energy of the hotcoals and ashes passing from the stoker and in position to be swept byair therethrough and in the path of the heated materials discharged fromthe Stoker, and a solenoid in series with the thermostat, said solenoidbeing so placed with respect to the stoker mechanism as to causereduction in the speed thereof upon closure of said circuit.

3. The combination in a furnace including an ashpit, of stoker controlmechanism for feeding fuel thru the `furnace and discharging to theashpit, comprising a tube mounted in said ashpit and normally open tothe atmosphere, a thermostat controlling said mechanism supported on theinner end of said tube and exposed to the radiant heat energyvof the hotcoals and ashes passing from the Stoker, thermostat adjusting meansmanually operable outside the furnace for establishing the temperatureat which a change in stoker speed becomes effective, the thermostatbeing positioned in the path of air drawn thru said tube and of theheated materials discharged from the stoker, and a solenoid in serieswith the ther mostat, said solenoid being so disposed with respect tothe stoker mechanism as to cause reduction in the speed thereof uponclosure of said circuit.

4. The `combination with a furnace and grate stoker mechanism forfeeding fuel therethrough, of means for controlling the rate of actionof said mechanism, comprising a thermal unit including a tube mounted ina furnace wall and open at one end to the atmosphere and at its otherend to a zone of the furnace adjacent the discharge end of the Stoker, athermostat supported on the inner end of said tube in position to beswept by air drawn therethrough and in the path of heated materialsdischarged from the. Stoker, and a solenoid in series with thethermostat, said solenoid being so placed with respect to the stokermechanism as to cause reduction in the speed thereof upon closure ofsaid circuit.

WILLIAM A. LACKE.

